With the development of broadband environments including x Digital Subscriber Lines and optical fibers, data communications using the Internet have become rapidly available in recent years, regardless of whether in companies or in households. Furthermore, home network environments have also become common, in which personal computers (simply referred to as “PC” hereinafter) and home appliances in households are connected via Ethernet®, a wireless LAN, or the like, In such environments, not only PCs, but also home appliances, such as a television, a DVD recorders an air conditioner, and a refrigerator can be connected with each other.
Furthermore, various applications may be implemented by enabling file transfer between a PC and a home appliance via the Internet or a home network. For example, such applications may include: an application that transfers an MPEG2 file stored in a DVD recorder to a PC and enables viewing and editing of the file; and an application that transfers an MPEG2 file stored in a DVD recorder to another DVD recorder and performs the back-up of the file (dubs the file), With these techniques, the user can handle data and the like freely without recognizing a location of the data or a location of a file.
However, when data under copyright restriction (referred to also as “copyright protection data”) is transmitted on a network, a technique for protecting copyright becomes necessary. Thus, Digital Transmission Content Protection over IP (DTCP-IP) has recently been suggested as a technique for preventing unauthorized copying of copyright protection data on a network. In the DTCP-IP, data is encrypted and then transmitted on a network. Furthermore, in the DTCP-IP, copy control information is specified for each data as follows: Copy Never that totally prohibits copying; Copy One Generation that allows copying only one-generation data; and Copy Free that allows free copying. In Copy One Generation, it is specified that a data transmission apparatus that is a data transfer source immediately deletes or invalidates data that has been transmitted to a data reception apparatus but is present in the data transmission apparatus, so that the same usable data may not be present in the transmission apparatus and the reception apparatus at the same time. Under such a condition, the data transmission apparatus is allowed to transfer (also referred to as “MOVE”) One Generation copied data to another device. In order to implement MOVE processing in compliance with the condition, the data needs to be transferred while maintaining a state that the same usable data is present neither in the data transmission apparatus at a data transmission side nor a data reception apparatus at a data reception side at the same time. Non-Patent References 1 and 2 disclose details of the aforementioned prior art.
A means for implementing “MOVE” processing on Copy-One-Generation data under the aforementioned condition has conventionally been studied (for example, refer to Patent Reference 1). According to the technique disclosed in Patent Reference 1, an apparatus that is a data transfer source encrypts and outputs data to an external recording apparatus that is a data transfer destination. After outputting the transfer-target data, the apparatus certainly moves the data by transmitting a decryption key of the data and deleting the data at the transfer source.    Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2002-290905    Non-Patent Reference 1: Digital Transmission Content Protection Specification Volume 1 (Informational Version)    Non-Patent Reference 2: Digital Transmission Protection License Agreement    Non-Patent Reference 3: DTCP Volume 1 Supplement E Mapping DTCP to IP (Informational Version)    Non-Patent Reference 4: RFC2616 Hypertext Transfer Protocol—HTTP/1.1